The present invention relates to energy meters with electronic registers, and more particularly to the provision of a method and apparatus for testing the operation of the optical electronics system when used in such meters.
Present-day electronic registers have greatly expanded capabilities and are being called upon to provide additional functions beyond simple measurements of kilowatthour energy consumption and kilowatt demand. The inclusion of microprocessors in electronic registers has provided the capability to provide a plurality of additional functions, and make additional information available to the customer, the meter reader and the serviceman. In electronic registers, it is well-known to utilize optical electronics to measure energy consumed by the load being metered. In a combination induction electric watthour meter and time of use or demand electronic register, the watthour meter utilizes an eddy current disk which rotates in response to the rate of energy consumption being metered. A shutter is commonly mounted on the same shaft as the eddy current disk and is positioned to rotate between a light emitter and a light detector. A plurality of circumferential teeth on the rotating shutter sequentially break the light beam between the light emitter and light detector to provide a series of electrical pulses which are directly proportional to the rate of energy consumption by the load being metered.
It is common practice to provide an optical communications link between the electronic register and the outside of the meter in order to provide an interface to a portable reader, providing an automatic means for extracting billing data and for programming the electronic register.
It is possible that the electronic circuitry associated with the disk sensing optics system may fail even though the eddy current disk continues to rotate and the induction watthour meter continues to properly display kilowatt hours of power consumed by the load being metered. A problem exists if a register light emitter should fail, particularly if this occurs shortly before the electronic register is read by the meter reader. For example, if meter readings are taken once a month and if one of the light emitters fails just prior to a particular meter reading, the absence of the time of use readings provided by the electronic register may not become apparent until the following month or other period when the register is next read. It is thus desirable to provide for the testing of the operation of the light emission circuitry in the disk sensing optics system of an electronic register, since this is more likely to fail than the induction watthour meter. This would provide the meter reader with an indication of the operation of the disk sensing optics system circuitry each time, and at the time, the electronic register is read and enable prompt corrective action. In particular, it is desirable to be able to determine whether the light emitter circuitry is operating at the time of meter reading, while at the same time minimizing the requirement for additional components and added complexity of the electronic register.
As with all energy meters, including energy meters with electronic registers, where the customer pays for energy consumption based on the meter readings, it is important to provide the ability to detect tampering attempts which can be anticipated. One form of tampering includes the use of high intensity light, particularly infrared light, which is directed from the outside of the energy meter towards the disk sensing optics assembly. Since energy consumption, or the rate of energy consumption, is detected in the disk sensing optics assembly by the rate at which the toothed shutter interrupts the light path between the light source and the light detector as it rotates between them, an extremely bright light shining on the light detector could interfere with the detector sensing interruptions of the normal operating light beam by the passage of teeth on the toothed shutter.
As a result, means are needed to detect whether there has been tampering with the electronic register through use of an extremely bright external light source. It is also highly desirable that this be accomplished simply, reliably, and efficiently.
In addition, it is desirable that the failure error signal be available at the electronic register for the information and use of the meter reader. It is desirable that the tamper error signal be stored within, but not available at, or displayed by, the electronic register. It is desirable that the tamper error signal be provided instead to the office of the power company for analysis and appropriate action, whether customer relations or legal action, as appropriate.